The British Guiana Museum. 229 
covered in these organisms. The glassy sponge exhibited 
is commonly known as Venus* flower basket (Euplec- 
tella) — a form found in large numbers in various parts 
of the world, especially in the Philippine Islands, often in 
deep w T ater. 
The corals form a very interesting group, since by their 
means have been built up whole series of islands in the East 
and West Indies — a process that is still going on ; while 
very large areas of the earth consist of their fossil remains. 
The coral animals, erroneously called "insects," are 
very like the soft-bodied sea-anemones, but instead of 
being single they form colonies ; and as they are able to 
take up the lime dissolved in sea-water and deposit it in 
their tissues, they form calcareous skeletons. By contin- 
uous growth upon a suitable position, they give rise to 
coral islands. The coral colonies take on very different 
shapes, being sometimes like mushrooms, as in the 
specimens ot Fungia in the case ; at other times they 
become tree-like, and are either hard and stony, or pliant, 
when they may be plaited into whips, as in the specimen 
shown in the case. Sometimes they form broad fans, as in 
the specimens of Venus' fan exhibited. The red coral, used 
for making necklaces etc., is the only form of commer- 
cial importance. In the living state, all the skeleton is 
covered with a thin fleshy layer in w T hich are seen the coral 
animals like flowers on a plant. The coral-builders live in 
warm water, being found in the tropics within 30 of the 
equator; they flourish best at depths of about 5— t2o 
fathoms , and being unable to live out of water, are found 
below tide mark ; while on the other hand they do not 
flourish at depths much exceeding 30 fathoms. They 
are an extremely ancient type of life, and are found 
GG 
